JP3369941B2 - Manufacturing method of electrical steel sheet for bonded iron core with excellent adhesive strength, corrosion resistance and blocking resistance - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to punching, shearing,
The present invention relates to a method for producing an electromagnetic steel sheet for an adhesive iron core, which is used by adhering by pressure / heating (thermocompression bonding) after processing such as press working.

[0002]

2. Description of the Related Art Iron cores generally used in electric equipment such as motors and transformers are manufactured by punching or shearing a magnetic steel sheet having an insulating coating on the surface to reduce eddy current loss. , Laminated and then fixed by welding, caulking or adhesive.

However, in the fixing method by welding or caulking, the insulating film is destroyed and the iron core is electrically short-circuited, which causes an increase in eddy current loss, and mechanical or thermal strain deteriorates the magnetic characteristics. It has the drawback of being prone to occur. In addition, in the fixing method using an adhesive, it is necessary to apply the adhesive to each of the punched or sheared steel sheets, which requires a lot of time and labor, resulting in poor work efficiency.

In contrast to the above-mentioned conventional technique, an adhesive type insulating film capable of obtaining an adhesive action by pressurizing and heating (thermocompression bonding) is formed on the surface of the magnetic steel sheet in advance, thereby omitting the adhesive applying step. An electromagnetic steel sheet for an adhesive iron core made possible is known, and the following techniques have been proposed for this. (1) Japanese Patent Publication No. 52-8988 discloses a surface-coated steel sheet for laminated iron core, which is obtained by applying a treatment liquid obtained by emulsifying a solvent-type thermoplastic resin and a thermosetting resin with an emulsifier to a steel sheet surface and then drying it. Has been done.

(2) Japanese Patent No. 2574698 discloses a thermoplastic acrylic resin emulsion (A) having a glass transition point of 60 ° C. or higher, an epoxy resin emulsion (B), an amine-based epoxy resin curing agent and a specific film-forming aid. A water-based adhesive type insulation coating composition containing an agent as a main component and having a resin solid content weight ratio of component (A) and component (B) of (A) / (B) = 70/30 to 95/5 is applied to a steel plate surface. A coated and dried magnetic steel sheet for a bonded iron core is shown.

(3) Japanese Patent Laid-Open No. 7-308990 discloses that
The main components are an acrylic emulsion resin (A) having a glass transition point of 80 to 130 ° C. and a functional group capable of reacting with an epoxy group in the molecule, and an epoxy resin emulsion (B) having a melting point or softening point of 70 to 140 ° C. And ingredient (A)
And the resin solid content weight ratio of the component (B) is (A) / (B) = 9.
Heating having a mixed resin film of 5/5 to 70/30 and having a gelation rate of the mixed resin film in the range of 10 to 90% by weight and showing sufficient adhesive strength even in a high temperature environment of 150 ° C. or higher. A surface coated electrical steel sheet for bonding is shown.

(4) Japanese Patent Application Laid-Open No. 7-268307 discloses that
A water-based heat-adhesive coating composition comprising a thermoplastic resin emulsion having a glass transition point of 80 ° C. or higher, an epoxy resin emulsion, and an aqueous phenol resin and having excellent high-temperature adhesive strength is disclosed. (5) In Japanese Patent No. 2529053, an acrylic resin emulsion and an epoxy resin emulsion which do not contain a nitrogen atom and a sulfur atom in a monomer, and an acid anhydride type epoxy curing agent which reacts with an epoxy resin or a methylol group-containing initial condensation A method for producing a surface-coated magnetic steel sheet for adhesion, which has less odor during coating and drying or aluminum die-casting, is characterized in that a mixed solution containing a substance as a main component is applied to the surface of the steel sheet and dried.

(6) Japanese Patent No. 2613725 discloses that an acrylic-modified epoxy resin emulsion in which a latent curing agent is preliminarily blended on the surface of a steel sheet (after the latent curing agent is blended in the epoxy resin, it is reacted with the acrylic resin to form an epoxy resin). It is characterized by coating the periphery of resin and latent curing agent, then applying a mixed solution containing the emulsion as the main component, and baking it in an incomplete state. A method for producing a surface-coated magnetic steel sheet for adhesion with low odor is shown.

[0009]

However, the surface-coated magnetic steel sheet for an adhesive iron core obtained by these conventional techniques has the following problems.
There are the following problems. The surface-coated steel sheet of (1) above,
About 40% or more of the base resin in the coating consists of a thermoplastic resin, so some adhesive strength at room temperature can be obtained, but under high temperature environment the thermoplastic resin softens and a sufficient level of adhesive strength is obtained. Absent. In addition, since a large amount of emulsifier is used for making it aqueous, it is also inferior in corrosion resistance.

In the above-mentioned (2) electromagnetic steel sheet for an adhesive iron core, 70% or more of the base resin in the coating is made of a thermoplastic resin.
Although the adhesive strength at room temperature can be obtained to some extent, a sufficient level of adhesive strength cannot be obtained due to softening of the thermoplastic resin in a high temperature environment. The surface-coated electromagnetic steel sheet in (3) above has 15
Although the adhesive strength in a high temperature environment of 0 ° C. or higher is improved, as is clear from the examples, the epoxy resin emulsion is emulsified by the forced emulsification method using an emulsifier, so that the emulsifier is formed in the film. The hydrophilic groups remaining in the emulsifier component cause a hygroscopic effect,
It has the disadvantage of poor corrosion resistance.

The adhesive type insulating film obtained by the water-based heat-adhesive type coating composition of the above (4) can provide sufficient adhesive strength when the film thickness is relatively thick, about 10 μm (dry film thickness). In the case of a relatively thin film thickness of 5 to 6 μm (dry film thickness) or less, sufficient adhesive strength cannot be obtained. Surface-coated electromagnetic steel sheet obtained by the manufacturing method of (5) above,
Although the generation of odor during coating and drying or during aluminum die casting is improved, a sufficient level of adhesive strength in a high temperature environment cannot be obtained. The surface-coated electrical steel sheet of (6) above is excellent in adhesive strength at room temperature and after long-term storage, but inferior in high temperature environment.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and, after being heat-pressed as an iron core material, have sufficient adhesive strength not only at room temperature but also at a high temperature of about 150 ° C. An object of the present invention is to provide a method for producing an electromagnetic steel sheet for an adhesive iron core, which is excellent in blocking resistance and corrosion resistance as the electromagnetic steel sheet for an adhesive iron core.

[0013]

[Means for Solving the Problems] The inventors of the present invention have keenly studied the relationship between the coating composition of an electrical steel sheet for an adhesive iron core and the manufacturing conditions thereof, and the adhesive strength, corrosion resistance, blocking resistance, etc. under normal temperature and high temperature environments. As a result of repeated studies, the following findings were obtained. 1) By using a specific resin mainly composed of an epoxy resin as a main component of the base resin constituting the coating composition, excellent adhesive strength under normal temperature and high temperature environments can be obtained. In particular, the morphology of the base resin in the coating composition has a great influence on the performance of the magnetic steel sheet for the adhesive iron core, and by using a specific water-dispersed resin as the base resin, particularly excellent adhesive strength and good corrosion resistance And blocking resistance can be obtained.

2) By using a phenol resin as a curing agent for a coating composition containing the above-mentioned specific resin as a base resin, the high temperature adhesive strength is effectively improved without deteriorating the blocking resistance and the corrosion resistance. Can be made. Furthermore, the high temperature adhesive strength is further improved by adding a phenol resin and a latent curing agent as a curing agent.

The present invention has been made on the basis of such findings, and its features are as follows. [1] As a resin component, a water-dispersible resin 1 shown in [i] below
A water-based coating composition containing a curing agent in an amount of 1 to 40 parts by weight (solid content) with respect to 00 parts by weight is applied to at least one surface of an electromagnetic steel sheet so as to have a dry film thickness of 1.0 to 12 μm. A method for producing an electromagnetic steel sheet for an adhesive iron core, which is excellent in adhesive strength, corrosion resistance and blocking resistance, characterized in that it is applied to a substrate and baked at an ultimate plate temperature of 100 to 300 ° C. [I] Grafted product (A) / (B) consisting of high molecular weight epoxy resin (A) and high molecular weight acrylic resin (B) in the following weight ratios: 55/45 to 95/5 (solid content weight ratio)

[2] In the production method of the above-mentioned [1], the number average molecular weight of the high molecular weight epoxy resin (A) constituting the water-dispersible resin is 1200 to 8000, the adhesive strength, the corrosion resistance and the resistance to corrosion. A method of manufacturing an electromagnetic steel sheet for an adhesive iron core having excellent blocking property. [3] In the manufacturing method according to the above [1] or [2], at least a part of the curing agent is a phenolic resin, which is excellent in adhesive strength, corrosion resistance and blocking resistance Production method.

[4] In the production method according to any one of the above [1] to [3], the curing agent comprises a phenol resin and a latent curing agent, and the latent curing is based on 100 parts by weight of the phenol resin in terms of solid content. A method for producing an electromagnetic steel sheet for an adhesive iron core, which is excellent in adhesive strength, corrosion resistance and blocking resistance, characterized in that the compounding amount of the agent is 2 to 200 parts by weight.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below together with the reasons for limitation. The object of the production according to the method of the present invention is an electromagnetic steel sheet for an adhesive iron core having an insulating film (adhesive insulating film) capable of obtaining an adhesive action by pressurizing and heating (thermocompression bonding). In the present invention, the steel plate serving as the substrate on which the adhesive insulating film is to be formed is an electromagnetic steel plate for iron core used in electric equipment such as motors and transformers. As such an electromagnetic steel sheet, a non-oriented electrical steel sheet or a grain-oriented electrical steel sheet is generally used, but in addition to this, a mild steel sheet, a stainless steel sheet, other special steel sheet, etc. may be used, and the steel sheet serving as a substrate is not limited. . The effects of the present invention can be obtained when any of these steel plates is used as the substrate.

The electromagnetic steel sheet used as a substrate has one or two kinds of surface treatment such as a zinc-based plating or other metal plating film, a chemical conversion treatment film, an inorganic or inorganic-organic insulating film, etc., on its surface in advance. In the present invention, the surface of the electrical steel sheet refers to the surface of the uppermost coating when these surface-treated coatings are provided.

In the production method of the present invention, a coating film is formed by applying a water-based coating composition containing a specific water-dispersible resin and a curing agent as main components on the surface of the above-mentioned magnetic steel sheet and baking it to form a film. A specific water-dispersible resin mainly containing an epoxy resin is used as the water-dispersible resin constituting the coating composition. As a result of the inventors' studying the relationship between various water-based resins that are the base resin of the water-based coating composition and the adhesive strength, an epoxy-based resin is the main resin of the base resin that constitutes the water-based coating composition. It turned out to be optimal.

[0021] The coating composition No. 49,
No. As shown in the comparative example using 50, when acrylic resin or urethane resin is used as the base resin of the water-based coating composition, the adhesive strength at room temperature is obtained, but sufficient adhesion is obtained in a high temperature environment. No strength is obtained. This is because the acrylic resin is a thermoplastic resin, which causes the film to soften at high temperatures, resulting in poor high-temperature adhesive strength, and the urethane resin tends to dissociate urethane bonds at high temperatures. It is considered that this is because sufficient high temperature adhesive strength cannot be obtained.

On the other hand, a film made of a base resin mainly composed of an epoxy resin and a curing agent therefor as used in the present invention exhibits excellent adhesive strength under both normal temperature and high temperature environments. This is because the epoxy resin and the curing agent form a three-dimensional crosslinked structure by thermocompression bonding during manufacturing of the iron core, and this crosslinked structure hardly causes softening of the film even in a high temperature environment.
It is considered that this is because excellent adhesive strength at high temperature can be obtained.

Further, the present inventors have examined the relationship between the morphology of the base resin in the water-based coating composition and the performance of the magnetic steel sheet for the adhesive iron core. The form of the epoxy resin in the water-based coating composition includes a water-soluble epoxy resin and an emulsifier that are made water-soluble by neutralizing at least a part of carboxyl groups after addition polymerization of polybasic acid and epoxy resin. There are emulsion-type epoxy resins that perform forced emulsification in the presence of water, and water-dispersion-type epoxy resins that use protective colloids of polar resins. However, according to a study by the present inventors, these water-soluble types as the base resin,
It has been found that the following problems occur when each emulsion type epoxy resin is used alone.

First, when a water-soluble type or an emulsion type epoxy resin is used alone as a base resin, it is impossible to secure a good balance of adhesive strength, corrosion resistance and blocking resistance. That is, the magnetic steel sheet for adhesive iron core, in the manufacturing stage, in order to obtain the desired adhesive strength during iron core production, the film is in a semi-cured state (the film is cured to an extent that blocking resistance and corrosion resistance are good. It is necessary to stop the curing reaction and bake into a state in which the curing reaction is completed and the desired adhesive strength is obtained only by thermocompression bonding during iron core production.

However, with water-soluble epoxy resins, it is difficult to obtain a high molecular weight required for the above-mentioned cured film in production. Therefore, water-soluble epoxy resin is used alone as the base resin. Even if the film used in (1) is baked in a semi-cured state as described above, a cured film having both blocking resistance and adhesive strength cannot be obtained because of the low molecular weight of the resin. Even if a high molecular weight water-soluble epoxy resin required for a cured film is obtained, a film using the water-soluble epoxy resin alone contains many ester groups. Since the ester group is liable to be hydrolyzed, the film easily absorbs moisture and has poor corrosion resistance. Further, when the emulsion type epoxy resin is used alone as the base resin, the adhesive strength and blocking resistance are excellent, but since a large amount of emulsifier is used, the film is likely to absorb moisture, resulting in poor corrosion resistance.

On the other hand, the case of using the above water-dispersible epoxy resin as the base resin was examined, and the following [i] which was a grafted product of the high molecular weight epoxy resin and the high molecular weight acrylic resin as the base resin It was found that a film having excellent adhesive strength, good corrosion resistance, and blocking resistance can be obtained by using the water-dispersible resin shown in [1] and optimizing the baking temperature and the amount of the curing agent. [I] Grafted product (A) / (B) consisting of high molecular weight epoxy resin (A) and high molecular weight acrylic resin (B) in the following weight ratios: 55/45 to 95/5 (solid content weight ratio)

The grafted product of the high molecular weight epoxy resin (A) and the high molecular weight acrylic resin (B), which is the water-dispersible resin, has a solid content weight ratio of (A) / (B) of 55/45 to.
95/5. When this weight ratio is less than 55/45, the ratio of the high molecular weight acrylic resin is excessive (the thermoplastic component is excessive), and therefore the adhesive strength under normal temperature and high temperature environments is poor. On the other hand, if the weight ratio exceeds 95/5, the base resin becomes difficult to disperse in the water-based coating composition, and the coating stability becomes poor. Further, in order to obtain particularly excellent high temperature adhesive strength,
The solid content weight ratio of (A) / (B) is 70/30 to 90/1.
It is desirable to set it to 0. When a water-dispersed epoxy resin other than the above graft product is used alone, a certain degree of adhesive strength can be obtained, but the adhesive strength level is not sufficient.

In the above graft product, the high molecular weight epoxy resin (A) preferably has a number average molecular weight of 1200 to 8000. When the number average molecular weight is less than 1200, it is not preferable because the corrosion resistance and adhesive strength of the film are poor, and when the number average molecular weight exceeds 8000, the coating stability is poor, which is not preferable. From this point of view, the more preferable number average molecular weight of the high molecular weight epoxy resin is 2000.
˜7,000, particularly preferably 2,500 to 7,000.

The number average molecular weight of the high molecular weight acrylic resin (B) is preferably about 5,000 to 100,000. If the number average molecular weight is less than 5,000, blocking resistance and adhesive strength are poor, which is not preferable. On the other hand, if the number average molecular weight exceeds 100,000, the coating composition has a high viscosity, which makes it difficult to apply it to a steel sheet.

The graft product of the high molecular weight epoxy resin (A) and the high molecular weight acrylic resin (B) can be obtained, for example, by the following method. (I) A high molecular weight epoxy resin and a carboxyl group-containing acrylic resin are subjected to ester addition reaction in an organic solvent solution in the presence of a tertiary amine. (II) In a solution of an organic solvent, a radical polymerizable unsaturated monomer is graft-polymerized with a high molecular weight epoxy resin in the presence of a radical generator such as benzoyl peroxide.

The high molecular weight epoxy resin used in the above reactions (I) and (II) is, for example, one obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of an alkali catalyst, epichlorohydrin and bisphenol with an alkali catalyst. In the presence of, a low molecular weight epoxy resin is condensed, and obtained by subjecting this low molecular weight epoxy resin and bisphenol to a polyaddition reaction, and the like. It may be. Examples of the dibasic acid of the general formula _{HOOC- (CH 2) n-COOH} ( wherein, n represents an integer of 1 to 12), a compound represented by is preferably used, specifically succinic acid, Examples include adipic acid, himelic acid, azelaic acid, sebacic acid, dodecanenic acid, hexahydrophthalic acid and the like. As bisphenol, bisphenol A and bisphenol F are preferably used, and these may be mixed and used.

The preferable number average molecular weight of the high molecular weight epoxy resin is as described above, and specific examples of such a high molecular weight epoxy resin include Epicoat 1004 (epoxy equivalent: about 90) manufactured by Shell Chemical Co.
0, number average molecular weight: about 1400), Epicoat 1007
(Epoxy equivalent: about 1700, number average molecular weight: about 290
0), Epicoat 1009 (epoxy equivalent: about 350
0, number average molecular weight: about 3750), Epicoat 1010
(Epoxy equivalent: about 4500, number average molecular weight: about 550
0) and the like. In addition, these high molecular weight epoxy resins can be used individually or in mixture of 2 or more types.

The number of epoxy groups per molecule of the high molecular weight epoxy resin constituting the grafted product is not particularly limited, but when a grafted product of the high molecular weight epoxy resin and the carboxyl group-containing acrylic resin is obtained, the reaction The number of epoxy groups is appropriately selected depending on the form. That is, when the reaction form is the ester addition reaction of (I) above,
The average number of epoxy groups per molecule of epoxy resin is 0.5-2.
The number is preferably 0, preferably 0.5 to 1.6. When the reaction form is a graft reaction of an acrylic monomer containing a carboxyl group-containing acrylic monomer by hydrogen abstraction of the epoxy resin main chain of the above (II), the epoxy group does not substantially exist in the epoxy resin. May be.

As the carboxyl group-containing acrylic resin used in the above (I) esterification reaction, at least one selected from the following carboxyl group-containing radically polymerizable unsaturated monomers of group [a] is polymerized. Alternatively, an acrylic resin obtained by copolymerization, or at least one selected from the following carboxyl group-containing radically polymerizable unsaturated monomers of the group [a] and a monomer of the group [a] are used. An acrylic resin obtained by copolymerizing at least one selected from the radically polymerizable unsaturated monomers of the following [b] group which are polymerizable can be exemplified.

[A] α or β ethylenically unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, etc. [b]: 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxy Acrylic acid or methacrylic acid, such as propyl acrylate and hydroxypropyl methacrylate, has 1 carbon atom
~ 8 hydroxyalkyl esters: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate,
n-butyl methacrylate, isobutyl acrylate,
Isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, decyl acrylate, etc. Alkyl or cycloalkyl esters of acrylic acid or methacrylic acid having 1 to 24 carbon atoms, such as: acrylamide, methacrylamide, N-methyl acrylamide, N-methyl acrylamide, diacetone acrylamide, N-methylol acrylamide,
Functional acrylic or methacrylamide, such as N-methylolmethacrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide, etc.,
: Aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, etc .: Vinyl propionate, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl propionate, vinyl pivalate, Veova monomer (manufactured by Shell Chemical Co.), etc. Vinyl monomer like

The following are examples of preferable combinations of the above unsaturated monomers. (A) Methyl methacrylate / 2-ethylhexyl acrylate / acrylic acid (b) styrene / methyl methacrylate / ethyl acrylate / methacrylic acid (c) styrene / ethyl acrylate / methacrylic acid (d) methyl methacrylate / acrylic acid Ethyl / acrylic acid

The above-mentioned carboxyl group-containing acrylic resin can be easily prepared, for example, by polymerizing or copolymerizing the above-mentioned unsaturated monomer by a solution polymerization method in the presence of a radical polymerization initiator. The number average molecular weight of the high molecular weight acrylic resin is as described above. Therefore, it is preferable that the carboxyl group-containing acrylic resin also has the same number average molecular weight. Also,
The acid value of the carboxyl group-containing acrylic resin is preferably in the range of about 50 to 500 in terms of resin solid content. If the acid value is less than 50, the coating stability of the coating composition is poor, which is not preferable.
On the other hand, when the acid value exceeds 500, the coating composition becomes highly viscous and it becomes difficult to apply it to the steel sheet.

The solid content concentration of the high molecular weight epoxy resin and the carboxyl group-containing acrylic resin used in the above (I) ester addition reaction is not particularly limited, but is preferably within the range having the optimum viscosity of these resins. . Further, the tertiary amine used in the ester addition reaction is preferably used in the range of usually 0.1 to 1 equivalent based on the epoxy group of the high molecular weight epoxy resin.

The above esterification reaction can be carried out by a conventionally known method, for example, after uniformly mixing an organic solvent solution of a high molecular weight epoxy resin and an organic solvent solution of a carboxyl group-containing acrylic resin, a tertiary amine About 1 to 6 at a reaction temperature of usually 60 to 130 ° C. in the presence of an aqueous solution.
The reaction for a period of time is preferably carried out until the epoxy groups are substantially consumed.

The radical-polymerizable unsaturated monomer used when the grafted product of the high molecular weight epoxy resin and the high molecular weight acrylic resin is obtained by the graft polymerization reaction of the above (II) is the ester addition reaction of the above (I). Examples of the radical-polymerizable unsaturated monomer of the above-mentioned [a] group and [b] group used for the production of the carboxyl group-containing acrylic resin used in Step 1. ] At least one selected from the group of carboxyl group-containing radically polymerizable unsaturated monomers, or at least one selected from the group [a] of carboxyl group-containing radically polymerizable unsaturated monomers; b group] at least 1 selected from radically polymerizable unsaturated monomers
Seeds are used.

In the above graft polymerization reaction, the mixing ratio of the high molecular weight epoxy resin and the radically polymerizable unsaturated monomer is not particularly limited, but the high molecular weight epoxy resin (A) in the finally produced graft product is used. The solid content weight ratio of the high molecular weight acrylic resin (B) is appropriately selected so as to fall within the above range. As the radical-polymerizable unsaturated monomer to be used, those containing a carboxyl group-containing radical-polymerizable unsaturated monomer in an amount of 20 to 80% by weight based on the total solid content of all radical-polymerizable unsaturated monomers. Particularly preferred. Further, the radical generator used in the graft polymerization reaction is
It is usually preferable to use it in the range of 3 to 15% by weight with respect to the radically polymerizable unsaturated monomer.

The above-mentioned graft polymerization reaction can be carried out by a conventionally known method, for example, a radical polymerizable unsaturated mixture obtained by uniformly mixing a radical generator with an organic solvent solution of a high molecular weight epoxy resin heated to 80 to 150 ° C. 1 to 3 monomers
It can be carried out by adding it over a period of time and then maintaining the same temperature for 1 to 3 hours.

The ester addition reaction of the above (I) and the above (I
As the organic solvent used in the graft polymerization reaction of I), a high molecular weight epoxy resin and a carboxyl group-containing acrylic resin are dissolved, and when the carboxylate of the reaction product of these resins is diluted with water, an emulsion solvent is used. Any water-miscible organic solvent that does not hinder the formation may be used, and any conventionally known organic solvent may be used as long as it is such an organic solvent.

Typical examples of such organic solvents include isopropanol, butyl alcohol, 2-hydroxy-
4-methylpentane, 2-ethylhexyl alcohol,
Examples thereof include alcohol solvents such as cyclohexanol, ethylene glycol, diethylene glycol, 1,3-butylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, cellosolve solvents and carbitol solvents. Further, it is also possible to use an inert organic solvent which is immiscible with water, and as such an organic solvent, for example, toluene, aromatic hydrocarbons such as xylene, ethyl acetate, esters such as butyl acetate, acetone, Examples include ketones such as methyl ethyl ketone.

The grafted product of the high molecular weight epoxy resin (A) and the high molecular weight acrylic resin (B) is made into a water dispersible resin by neutralizing at least a part of the carboxyl groups in the resin with a basic compound. be able to. As the basic compound used for neutralizing the carboxyl group, conventionally known compounds can be widely used. For example, any primary amine, secondary amine, tertiary amine, quaternary ammonium can be used. Salt etc. are mentioned.

Specifically, methylamine, ethylamine, n-propylamine, isopropylamine, n-hexylamine, monoethanolamine, propanolamine, benzylamine, dimethylamine, dibutylamine, dihexylamine, methylethanolamine, diethanolamine. , Triethylamine, diethylethanolamine, dimethylcyclohexylamine, triethanolamine, tributylamine, dimethyl n-butylamine, tripropylamine, γ-picoline, tetrahexyl ammonium hydroxide, and the like. The amount of such a neutralizing agent used is usually 0.1 to 2 with respect to the carboxyl group in the reaction product. The neutralization treatment with this neutralizing agent can also be performed by a conventionally known method.

As the curing agent used in the coating composition, a generally used epoxy resin curing agent can be used. For example, aliphatic polyamine, alicyclic polyamine, aromatic polyamine, polyamide polyamine, modified polyamine and the like can be used. Polyamine curing agents such as; monofunctional acid anhydrides (phthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic acid anhydride, chlorendic anhydride, etc.), 2
Functional acid anhydrides (pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, ethylene glycol bis (anhydrotrimate), methylcyclohexene tetracarboxylic acid anhydride, etc.), free acid anhydrides (trimellitic anhydride, poly Acid anhydride type curing agents such as azelaic acid anhydride); methylol group-containing initial condensates such as novolac or resol type phenolic resins, urea resins, melamine resins; latent curing agents, etc. At least one of the above can be used.

The content of the curing agent in the coating composition is 1 to 40 parts by weight based on 100 parts by weight of the water-dispersible resin in terms of solid content. If the compounding amount of the curing agent is less than 1 part by weight, sufficient curing is not performed during thermocompression bonding, resulting in poor adhesive strength. Also,
If the compounding amount of the curing agent exceeds 40 parts by weight, the coating composition is thickened and the film-forming property is deteriorated, so that the corrosion resistance and the adhesive strength are deteriorated.

As the curing agent, a phenolic resin is particularly preferable because the adhesive strength in a high temperature environment is remarkably improved. It is considered that this is because the heat resistance of the coating is improved by introducing a benzene ring into the coating. Examples of the phenol resin include a resol-type phenol resin having a methylol group introduced by condensation reaction of phenol such as phenol or bisphenol A with formaldehyde in the presence of a reaction catalyst.

For example, it is selected from 1 mol of bisphenol compound and 4 to 10 mol of formaldehyde, or unsubstituted monohydric phenol, p-substituted monohydric phenol, or o-substituted monohydric phenol with respect to 1 mol of bisphenol compound. 1 mol of phenols, which is a mixture of one or more monohydric phenols in a ratio of 0.5 mol or less in total, and 4 to 10 mol of formaldehyde, are reacted at a reaction temperature of 5 in the presence of a basic catalyst.
A resol-type phenol resin obtained by reacting at 0 to 60 degrees at a pH of 8.0 to 9.0 in the reaction system can be used.

Further, the combined addition of the phenol resin and the latent curing agent in a specific ratio further improves the adhesive strength of the film. That is, a phenolic resin and a latent curing agent are added together as a curing agent, and the compounding amount of the latent curing agent is 2 to 200 parts by weight, and particularly preferably 3 to 100 parts by weight based on 100 parts by weight of the phenol resin. By using the weight part, the adhesive strength is further improved.

In order to investigate the proper range of the compounding amount of the latent curing agent when the phenol resin and the latent curing agent are added in combination, the base resin (the base resin shown in Table 1 Resin No. 8): 100 parts by weight (solid content), phenol resin (phenol resin shown in Table 3): 5 parts by weight (solid content), and phenol resin 100
An aqueous coating composition in which the compounding amount (solid content) of the latent curing agent (latent curing agent shown in Table 3) with respect to parts by weight was changed was applied so that the dry film thickness was 6 μm, and the ultimate plate temperature was 200 ° C. An electromagnetic steel sheet for an adhesive iron core was prepared by baking, and the influence of the compounding amount of the latent curing agent on the high-temperature adhesive strength (this high-temperature adhesive strength was evaluated by the evaluation method described in Examples described later) was examined.

The results are shown in FIG. According to the figure, even if the compounding amount of the latent curing agent with respect to 100 parts by weight of the phenol resin is less than 2 parts by weight or exceeds 200 parts by weight,
No remarkable high temperature adhesive strength has been obtained by the combined addition of the phenolic resin and the latent curing agent. Further, particularly, the compounding amount of the latent curing agent is 3 to 100 parts by weight of the phenol resin.
The best high temperature adhesive strength is obtained in the range of 100 parts by weight.

As the latent curing agent used in the present invention,
Dicyandiamide, melamine, organic acid dihydrazide, amine imide, ketimine, tertiary amine salt, imidazole salt, boron trifluoride amine salt, microcapsule type curing agent (encapsulating the curing agent in microcapsules formed with casein, etc. A micro-capsule that breaks by pressure and undergoes a curing reaction with the resin), a molecular sieve type curing agent (a curing agent adsorbed on the surface of an adsorbing compound, which releases adsorbed molecules by heating and undergoes a curing reaction with the resin. Stuff) and the like.

The coating composition used in the present invention contains a base resin composed of the above-mentioned specific water-dispersible resin and a curing agent as main components. In the coating composition, in addition to the above-mentioned base resin component, Does not prevent inclusion of some other base resin components, for example, acrylic resin, polyurethane resin, polyamide resin, polyimide resin, polyester resin, sill cone resin, fluorine resin, polyethylene, polypropylene Such as synthetic resin, nylon,
Polysulfide, nitrile rubber, chloroprene rubber,
An elastomer such as polyvinyl formal may be contained in an amount of 35% by weight or less based on the resin component of the coating composition. In addition to these, oxide fine particles such as silica and alumina, a conductive substance, a rust preventive additive such as a poorly soluble chromate, a coloring pigment (for example, a condensed polycyclic organic pigment, a phthalocyanine organic pigment, etc.), It is also possible to blend one or more of coloring dyes (for example, azo dyes, azo metal complex salt dyes, etc.), film forming aids, dispersibility improving agents, defoaming agents and the like.

In the production method of the present invention, the coating composition is applied to the surface of an electromagnetic steel sheet and baked to form a film for laminating adhesion, which has a dry film thickness of 1.0 to
12 μm. When the film thickness is less than 1.0 μm, the adhesive strength is insufficient, while when the film thickness exceeds 12 μm, not only the adhesive strength is saturated, but also the space factor decreases, which is not preferable. From the viewpoint of such adhesive strength and space factor, a more preferable film thickness is 3 μm to 7 μm.

The method of applying the coating composition to the steel plate surface is arbitrary. Usually, it is applied by a roll coater method, but it is also possible to adjust the application amount by an air knife method or a roll drawing method after applying by a dipping method or a spray method. The baking treatment after applying the coating composition can be performed using a hot air oven, a high frequency induction heating oven, an infrared oven, or the like. The baking temperature is 100 to 300 ° C. as the ultimate plate temperature. When the reached plate temperature is less than 100 ° C., the coating film is not sufficiently hardened before thermocompression bonding for manufacturing the iron core, resulting in poor corrosion resistance and blocking resistance. On the other hand, the reached plate temperature is 300
If the temperature is higher than 0 ° C, the coating before thermocompression bonding will be excessively hardened, and the coating will not sufficiently soften and melt during thermocompression bonding, so that the interfaces between the coatings will not be melted together, resulting in poor adhesive strength. From this point of view, a more preferable baking temperature is 130 to 230 ° C., whereby particularly excellent adhesive strength, corrosion resistance and blocking resistance can be obtained.

The rate of temperature rise during the baking treatment is not particularly limited, but is preferably about 3 to 80 ° C./sec. Temperature rising rate is 3
If it is less than 80 ° C / sec, the production efficiency of the steel sheet is poor, which is not preferable. On the other hand, if it exceeds 80 ° C / sec, the coating film may be cracked, and the appearance of the coating film tends to deteriorate.

[0059]

[Example] A magnetic steel sheet having a thickness of 0.5 mm was coated with a coating composition by a roll coater and then baked to produce a magnetic steel sheet for an adhesive iron core, and the adhesive strength of the obtained electromagnetic steel sheet for an adhesive iron core was obtained. , Blocking resistance, and corrosion resistance were evaluated. Also,
The paint stability of the paint composition was also evaluated. The composition of the base resin used in the coating composition is shown in Tables 1 and 2, the curing agent is also shown in Table 3, the composition of the coating composition and the evaluation results of the coating stability are shown in Tables 4 to 6, for the adhesive iron core. Table 7 shows the manufacturing conditions (baking temperature and dry film thickness) of electromagnetic steel sheets and the results of performance evaluation.
It shows in Table 11. The method for preparing the coating composition and the method for evaluating each performance of the magnetic steel sheet for the adhesive iron core are shown below.

[Preparation of coating composition] [1.] Preparation of water-dispersible resin [1.1.] Method of producing water-dispersible resin by ester addition reaction Organic solvent solution of aromatic epoxy resin and carboxyl group-containing acrylic resin After being uniformly mixed with the organic solvent solution of 1., the ester addition reaction is carried out in the presence of a tertiary amine aqueous solution at a reaction temperature of 60 to 130 ° C. for about 1 to 6 hours to obtain a water-dispersible resin. As a specific manufacturing example, the base resin No. The method for producing the water-dispersible resin of No. 5 is as follows (a) to
It shows in (c).

(A) Production of high molecular weight epoxy resin solution In a reactor equipped with a reflux condenser, stirrer, thermometer and nitrogen gas blowing device, Epicoat 828 (epoxy resin manufactured by Yuka Shell Co., epoxy equivalent 184- 194) 5
When 00 parts, 286 parts of bisphenol A, 0.5 parts of tri-n-butylamine and 86 parts of methyl isobutyl ketone were charged and heated to 135 ° C under a nitrogen stream, the contents generated heat to 180 ° C. Cool it to 160 ° C,
The reaction was carried out for about 3 hours to obtain a 90% epoxy resin solution having an epoxy value of 0.025 and a melt viscosity (Gardner-Holt viscosity of a butyl carbitol solution of 40% resin at 25 ° C.) Z8.

(B) Production of Acrylic Resin Solution Containing Carboxyl Group 400 parts of butanol was collected in a four-necked flask equipped with a reflux condenser, a stirrer, a thermometer, a dropping funnel and a nitrogen inlet. Methacrylic acid 174 parts, styrene 87 parts, ethyl acrylate 29 parts and benzoyl peroxide (7
14.5 parts (5% water wet product) was collected in a beaker, mixed well and stirred to prepare a premixture. The temperature of butanol in the flask was heated to 105 ° C., at which temperature the premix was added dropwise from the dropping funnel over 3 hours. The temperature was maintained for another 2 hours to complete the copolymerization reaction. Then, 290 parts of 2-butoxyethanol was added to obtain a carboxyl group-containing acrylic resin solution having a viscosity of 370 centistokes, a resin acid value of 400, and a solid content of 30%.

(C) Production of water-dispersible resin The following (1) to (4) were placed in a reaction vessel and 115 ° C. under a nitrogen stream.
Then, the resin component was dissolved. After dissolution, the mixture was cooled to 105 ° C, the following (5) and (6) were added in this order, and the mixture was kept at 105 ° C for 3 hours. At the end of this reaction, the acid value was 51. Next, the following (7) was added over 30 minutes to obtain a stable water-dispersible resin having a solid content of 25%. (1) Epoxy resin solution obtained in (a) 267 parts (2) Acrylic resin solution obtained in (b) 200 parts (3) n-Butanol 66 parts (4) 2-Butoxyethanol 47 parts (5) Deionized water 3.2 parts (6) Dimethylaminoethanol 5.3 parts (7) Deionized water 612 parts

[1.2.] Production Method of Water-Dispersion-Type Resin by Graft Polymerization Reaction The method for producing the water-dispersible resin of No. 19 is shown below. The following (1) to (3) were placed in a reactor equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing device, and heated to 115 ° C under a nitrogen stream to dissolve the resin component. Then, the mixture of (4) to (7) was added dropwise over 1 hour,
Further, the mixture was reacted at 115 ° C. for 2 hours. Then, after cooling to 80 ° C, the following (8) was added, and while maintaining the temperature at 80 ° C, the following (9) was gradually added over 30 minutes under stirring to stabilize the solid content of 30%. A water-dispersible resin was obtained. (1) Epoxy resin solution obtained in (a) of the above [1.1.] 283 parts (2) n-butanol 121 parts (3) 2-butoxyethanol 117 parts (4) Methacrylic acid 27 parts (5) Styrene 13 .5 parts (6) Ethyl acrylate 4.5 parts (7) Benzoyl peroxide 3 parts (8) Dimethylaminoethanol 14.8 parts (9) Deionized water 416.2 parts

[2.] Hardener Table 3 shows the hardener used in the coating composition. [3.] Preparation of coating composition The base resins shown in Tables 1 and 2 and the curing agents shown in Table 3 were used, and these were mixed and stirred, and the Nos. Shown in Tables 4 to 6 were used.
1-No. 48 coating compositions were obtained. The proportion of non-volatile components in these coating compositions was all 20 wt%.

In addition, No. No. 49 acrylic resin emulsion and No. 49. The urethane resin emulsion of 50 was obtained by the following. (a) Acrylic resin emulsion: A monomer mixture consisting of 90 parts by weight of methyl methacrylate, 15 parts by weight of styrene, 10 parts by weight of acrylic acid and 10 parts by weight of ethyl acrylate was emulsion polymerized in water by a conventional method to prepare an acrylic resin emulsion. (b) Urethane resin emulsion: "Adeka Bonder HUX-240" manufactured by Asahi Denka Co., Ltd. was used.

[Evaluation of Paint Stability] The paint composition was tested at 40 ° C.
The sample was allowed to stand still and evaluated by the time until the gelation of the paint or the start of precipitation. The evaluation criteria are shown below. ○: 120 hours or more △: 24 hours or more, less than 120 hours ×: less than 24 hours

[Evaluation of Performance of Magnetic Steel Sheet for Adhesive Iron Core] (a) Film of magnetic steel sheet for adhesive iron core cut to a size of 25 mm × 50 mm in room-temperature adhesive strength so that the overlapping portion becomes 25 mm × 12.5 mm Overlapping formation surfaces, pressure 10kgf
In the state of pressurizing at / cm ² , thermocompression bonding was performed according to the temperature rising pattern shown in FIG. This was pulled by a tensile tester in a normal temperature atmosphere, the maximum load until breaking was measured, and the adhesive strength was evaluated by the tensile shear strength obtained by dividing the maximum load by the shear cross-sectional area (bonding area). The evaluation criteria are shown below. ◎: 160 kgf / cm ² or more ○ +: 140 kgf / cm ² or more, 160 kgf / cm ²
Less than ○: 120 kgf / cm ² or more, 140 kgf / cm ²
Less than △: 100 kgf / cm ² or more, 120 kgf / cm ²
Less than ×: less than 100 kgf / cm ²

(B) High temperature adhesive strength A sample prepared by the same method as the evaluation test of room temperature adhesive strength according to the above (a) and thermocompression bonded was pulled by a tensile tester in an atmosphere of 150 ° C., and the maximum load until breaking was measured. The maximum load was measured and the adhesive strength was evaluated by the tensile shear strength obtained by dividing the maximum load by the shearing area (bonding area). The evaluation criteria are shown below. ◎: 80kgf / cm ² or more ○ +: 60kgf / cm ² or more and less than ^{80kgf / cm 2 ○: 40kgf /} cm 2 or more and less than ^{60kgf / cm 2 △: 20kgf /} cm 2 or more, 40kgf / cm ² less than ×: 20kgf </ Cm ²

(C) Blocking resistance The film forming surfaces of the magnetic steel sheets for adhesive iron cores cut into a size of 20 mm × 20 mm are overlapped with each other, and a pressing force of 250 k is applied.
After pressurizing with gf / cm ² and leaving it in an atmosphere of 50 ° C. for 24 hours, the presence or absence of blocking was examined. The evaluation criteria are shown below. ○: without blocking ×: with blocking

(D) Corrosion resistance A salt spray test was conducted, and the area ratio of red rust after 24 hours was evaluated. The evaluation criteria are shown below. ◎: Red rust occurrence area ratio less than 10% ○: Red rust occurrence area ratio 10% or more, less than 25% △: Red rust occurrence area ratio 25% or more, less than 50% ×: Red rust occurrence area ratio 50% or more

[0072]

[Table 1]

[0073]

[Table 2]

[0074]

[Table 3]

[0075]

[Table 4]

[0076]

[Table 5]

[0077]

[Table 6]

[0078]

[Table 7]

[0079]

[Table 8]

[0080]

[Table 9]

[0081]

[Table 10]

[0082]

[Table 11]

[0083]

As described above, according to the present invention, a stable adhesive strength can be obtained even under the use environment of a motor or a transformer (normal temperature to high temperature), and the blocking resistance and the corrosion resistance are excellent. It is possible to manufacture a magnetic steel sheet for an adhesive iron core having a coating.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of the compounding amount of a latent curing agent with respect to 100 parts by weight of a phenol resin on the high temperature adhesive strength when a phenol resin and a latent curing agent are added together as a curing agent in a coating composition.

FIG. 2 is a drawing showing a temperature rise pattern of thermocompression bonding of an electromagnetic steel sheet for an adhesive iron core performed in an example.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI B05D 7/24 B05D 7/24 302U H02K 15/12 H02K 15/12 A (72) Inventor Sagiyama Katsu Marunouchi 1-chome, Chiyoda-ku, Tokyo 1-2 No. 2 Nippon Steel Pipe Co., Ltd. (72) Inventor Yoshio Imazaki 33-1 Kanzaki-cho Amagasaki-shi, Hyogo Prefecture Kansai Paint Co., Ltd. (72) Inventor Sumio Ezaki 33-1 Kanzaki-cho, Amagasaki-shi Kansai Kansai (56) References Japanese Patent Laid-Open No. 2-208034 (JP, A) Japanese Patent Laid-Open No. 5-185029 (JP, A) Japanese Patent Laid-Open No. 5-237968 (JP, A) Japanese Patent Laid-Open No. 6-182296 ( JP, A) JP 6-60443 (JP, A) JP 7-308990 (JP, A) JP 7-336969 (JP, A) JP 8-24779 (JP, A) JP 52-8998 (JP, B2) (58) Survey The field (Int.Cl. ^7, DB name) B32B 1/00 - 35/00 B05D 3/00 - 3/14 B05D 5/00 - 5/26 H02K 15/00 - 15/16

Claims (4)

(57) [Claims] 1. A water-based coating composition containing, as a resin component, a curing agent in a proportion (solid content) of 1 to 40 parts by weight with respect to 100 parts by weight of a water-dispersible resin shown in [i] below. , 1.0 to 1 in dry film thickness on at least one side of the electromagnetic steel sheet
Apply it to 2 μm, and reach the ultimate plate temperature of 100-300
Bonding strength, characterized by baking so that the temperature becomes
A method for producing an electromagnetic steel sheet for an adhesive iron core, which is excellent in corrosion resistance and blocking resistance. [I] Grafted product (A) / (B) consisting of high molecular weight epoxy resin (A) and high molecular weight acrylic resin (B) in the following weight ratios: 55/45 to 95/5 (solid content weight ratio) 2. The excellent adhesive strength, corrosion resistance and blocking resistance according to claim 1, wherein the high molecular weight epoxy resin (A) constituting the water-dispersible resin has a number average molecular weight of 1200 to 8000. For manufacturing magnetic steel sheets for bonded iron cores. 3. The method for producing an electromagnetic steel sheet for an adhesive iron core having excellent adhesive strength, corrosion resistance and blocking resistance according to claim 1, wherein at least a part of the curing agent is a phenol resin. 4. The curing agent comprises a phenolic resin and a latent curing agent, and the amount of the latent curing agent is 2 to 200 parts by weight based on 100 parts by weight of the phenol resin in terms of solid content. A method for producing an electromagnetic steel sheet for an adhesive iron core, which is excellent in adhesive strength, corrosion resistance and blocking resistance according to claim 1, 2 or 3.